Island



(No Model.)

B. H. RICH,

VACUUM DASH POT FOR ENGINES.

No. 546,976. Patented Sept. 24, 1895.

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RICHARD H. RICE, OF PROVIDENCE, RHODE ISLAND, ASSIGNOR TO THE RICE & SARGENT ENGINE COMPANY, OF SAME PLACE.

VACUUM DASH-POT FOR ENGINES.

SPECIFICATION forming part of Letters Patent No. 545,976, dated September 24, 1895.

Application filed April 27, 1895. Serial No. 547,402. (No model.)

To all whom it may concern:

Be it known that I, RICHARD H. RICE, a citizen of the United States, residing at Providence, in the State of Rhode Island, have invented a new and useful Improvement in Vacuum Dash-Pots for Steam-Engines, of which the following is a specification.

In dash-pots as ordinarily constructed the quantity of air retained in the passage leading to the relief-valve operates to prevent the proper closing action of the vacuum-cylinder, and it is the object of my invention to so construct the relief-valve that the space occupied by the air-passage may be reduced to a minimum, with a large area exposed to the action of the combined air; and it consists in the employment of a relief-valve having a passage of asrnall diameter communicating with the interior of the vacuum-cylinder and a large area for the action of the confined air to raise the relief-valve from its seatand a greater area exposed to the action of the confined air when the valve is in its raised condition.

In the accompanying drawings, Figure 1 represents a partial side elevation and axial section of a dash-pot embodying my invention. Fig. 2 represents an enlarged axial section of the relief-valve. Fig. 3 represents a similar enlarged section, showing a modification. Fig. A represents an inner end view of the valve shown in Fig. 3.

In the drawings, A represents the moving cylinder of the dash-pot, and B the vacuumplunger within the cylinder A. The outer flanged portion a of the cylinder A forms an annular piston C, which fits the outer cylinder D, and serves upon the upward movement of the cylinder A to draw the air for cushioning the said cylinder upward from under the flap-valves b 5 into the chamber of the cylinder D, the air so drawn in at the upward movement of the cylinder A being upon the downward movement of the said cylinder first expelled rapidly through the opening 0 in the side of the cylinder D into the air-passage at until the face of the annular piston C passes the opening 0, the piston C being thereafter cushioned to slower downward movement by the comparatively slow escape of the confined air, through the annular valve opening U, whereby the momentum of the cylinder A and its attachments will be properly checked.

In order to secure the proper action of the dash-pot, it is necessary to produce as perfect a vacuum as possible between the face (2 of the plunger B and the abutting facef of the vacuum-cylinder A, and this is to be accomplished by forcing out the small quantity of air which leaks inward around the plunger B at every stroke of the cylinder of the dashpot, which air would otherwise be liable to accumulate in the space between the face of the vacuum-plunger and the head of the cylinder, thus materially diminishing the available pressure upon the cylinder to effect the proper active closing of the steam-valve, and in order to properly expel the air which leaks inward at each stroke of the vacuum-cylinder I provide a valve-seat bushing E, having an external screw-thread g, and screw the same into the side of the vacuum-cylinder A, so that the central opening or passage h of the relief-valve F, held in the bushing, will lie in the plane of the face f 0f the head of the vacuum-cylinder, so that the air inclosed between the abutting surfaces eand f may be able to escape outward from the vacuum-cylinder A under the valve F, and in order to provide a relief-vale which will act under a light internal pressure of air at the extreme closing movement of the vacuum-cylinder I provide the bushing E with a backward miter t, which forms an annular valve-seat, and pro vide the valve F with the stem j, fitting the opening it in the bushing E, the said stem being provided with the central air-passage h, at the outer end of which are made the lateral openings h it, through which the air can pass to the extended narrow annular space Z between the inner face on of the valve F and the outer face of the bushing E, and by this means the required extended area for raising the valve may be obtained with an air-space reduced to its minimum.

The face at of the valve F is provided with the annular flange a, beveled reversely at its inner side to fit the backwardly-beveled annular valve seat 2', formed at the outer edge of the bushing E, and the valve F is held to its seati by means of the fiat spring 0, se

cured to the side of the cylinder A by means of the screws 13 19.

hen the valve F is thrown open by the pressure of the contained air in the vacuumcylinder at the extreme closing movement upon the vacuum-plunger, the elevated valve will present a greater area to the pressure of the air than when in its closed condition, the area of a variable portion of the reverselybeveled annular surface 5 being in this case effectively added to that of the inner surface m, thus allowing the valve to remain open until the pressure within the air-passage h has become considerably less than that required to cause the initial raising of the valve.

A modification of my invention is shown in Figs. 3 and 4c, in which the valve-stem j is provided with the small grooves r '7' upon its outer surface, instead of the central air-passage 71, the required communication being thus formed with the narrow annular space Z between the inner face m of the valve and the outer face of the bushing E, the operation of the valve being in this case the same as that before described.

The accumulated air-pressu re when the valve is in its closed condition is confined to the area included between the dotted lines a: a: of Figs. 2 and 3, and in its raised condition is extended to the perpendicular intersection of the dotted lines y y with the reverselymitered surface s of the valve F, as shown in Fig. 3, thus including an additional area consisting of the annular surface 20, embraced between the said lines as y, and the extent of such additional surface will be governed by the lifting height of the valve from its seat.

I claim as my invention- 1. In a vacuum dash-pot for closing the valves of an engine, the combination of the vacuum-cylinder with its plunger, and a relief-valve having a small air passage communicating with the interior of the vacuum-cylinder, and an extended area between the said air-passage and the valve-seat, for the action of the confined air, substantially as described.

2. In a vacuum dash-pot for closing the valves of an engine, the combination of the vacuum-cylinder, with its plunger, the bushing provided with a backwardly beveled annular valve-seat, and a relief-valve having a small air passage communicating with the interior of the vacuum-cylinder and an extended area between the said air-passage and the beveled annular valve-seat, substantially as described.

3. In a vacuum dash-pot for closing the valves of an engine, the relief-valve havinga small passage communicating with the vacuum-cylinder, an extended area for the action of the accumulated pressure of the confined air, and the baekwardly inclined annular valve-seat whereby the valve will present an increased area for the action of the confined air, when lifted from its seat, substantially as described.

RICHARD H. RICE.

\Vitnesses:

SOCRATES ScHoLFIELD, J. W. SARGENT. 

